Answer: The most common subtype of bipolar disorder is bipolar I disorder. And, this is a classic illness where you have alternating episodes of mania -- which are periods of extreme activity, and high energy and lack of sleep -- and depression -- which are periods depressed mood, and usually low energy and pessimism. And, the episodes here are severe, and when somebody has a manic episode they typically cannot function. They can be either very aggressive or euphoric and have really, really very strange and distractive behaviors at times.

When they are depressed, the depression can be also severe and people can be hospitalized, and can become suicidal. The second form of the illness is called bipolar II disorder, and here people have less severe episodes of mania, which are called hypomania, alternating with depression. And in this form of illness, when people are hypomanic, they often feel good and they work and they can be productive and can make a lot of money and do well for their families. And when they become depressed, the depression can be equally severe as if this was bipolar I disorder.

And the third most common form of the illness can be called mixed bipolar illness, and in this form people who have bipolar disorder have symptoms of mania and depression at the same time. They can be irritable or angry and depressed at the same time. This form of illness usually happens later in life and is somewhat more difficult to treat.